Hydraulic vibration-damping support

ABSTRACT

A hydraulic vibration-damping support comprising two strength members interconnected by an elastomer body defining in part a working chamber filled with liquid, the working chamber communicating via a constricted passage with a compensation chamber separated from the working chamber by a rigid partition. The rigid partition is provided with two gratings between which a decoupling valve member is mounted with clearance, which decoupling valve member is provided with studs disposed so that the decoupling valve member has a midplane disposed on a slant relative to the gratings.

FIELD OF THE INVENTION

The present invention relates to hydraulic vibration-damping supportsserving, for example, for mounting motor vehicle engines on the bodiesof such vehicles.

More precisely, in a first aspect, the invention relates to a hydraulicvibration-damping support serving to interconnect first and second rigidelements so as to damp and filter vibration between said elements, thesupport comprising:

first and second rigid strength members serving to be fixed torespective ones of the first and second rigid elements to beinterconnected;

an elastomer body interconnecting the first and second strength members;

a first chamber filled with liquid, and defined at least in part by theelastomer body; and

a decoupling device comprising firstly first and second parallelgratings that are generally plane in shape, and secondly a decouplingvalve member which is in the form of an elastomer pad and which hasfirst and second faces provided with projecting studs made of elastomer,the decoupling valve member being mounted with clearance between thefirst and second gratings with the first and second faces of saiddecoupling valve member disposed facing respective ones of the first andsecond gratings, and said decoupling valve member being suitable forclosing off said gratings, said first grating communicating with thefirst chamber and the second grating communicating with a second chambersuitable for enabling the decoupling valve member to vibrate freelybetween the two gratings when the first and second strength members aresubjected to relative vibratory movements (in practice, the secondchamber is usually constituted by a compensation chamber filled withliquid and connected to the first chamber via a constricted passage, butit may optionally be some other deformable hydraulic chamber or indeed apneumatic chamber).

BACKGROUND OF THE INVENTION

Document FR-A-2 674 590 describes an example of such a vibration-dampingsupport which operates quite satisfactorily, in particular to avoid orto limit banging of the valve member against the gratings, whichgenerates vibration and/or noise that is unpleasant for the users of thevehicle.

OBJECTS AND SUMMARY OF THE INVENTION

However, it has become apparent that it would be useful to improvevibration-damping supports of this type, in particular to achievefurther improvement in their performance.

To this end, in the first aspect of the invention, in avibration-damping support of the type in question the studs of thedecoupling valve member are disposed so that, in the absence of relativevibration between the first and second strength members, the decouplingvalve member is held in a rest position in which said valve member has amidplane disposed on a slant relative to the first and second gratings.

In preferred embodiments of the vibration-damping support in the firstaspect of the invention, it is optionally possible, in addition, to useany of the following provisions:

the studs of the decoupling valve member comprise outer studs which aredisposed in the vicinity of an outer periphery of said decoupling valvemember and which are distributed in first and second groups of outerstuds disposed on either side of a geometrical construction lineextending across the decoupling valve member parallel to the midplane ofsaid decoupling valve member, the first group of outer studs beingsituated on the first face, and the second group of outer studs beingsituated on the second face of said decoupling valve member;

the decoupling valve member is in the shape of a circular disk having acenter through which a diametrical line constituting said constructionline passes;

the outer studs of the first group are symmetrical to the outer studs ofthe second group about said construction line;

the decoupling valve member is provided with first and second elastomercentering lugs disposed at the center of the decoupling valve member onrespective ones of the two faces of said decoupling valve member, saidfirst and second centering lugs co-operating with respective ones of thetwo gratings to center the decoupling valve member relative to saidgratings, the studs of the decoupling valve member further comprisinginner studs disposed in the vicinity of the center of said decouplingvalve member on both faces of said decoupling valve member;

the decoupling valve member is provided with two inner studs disposed inthe vicinity of the first centering lug, symmetrically about saidconstruction line;

the second centering lug is clipped into one of the gratings, and thedecoupling valve member is provided with two inner studs disposed closeto the second centering lug, on the side of said construction lineopposite to its side on which the outer studs of the second group aresituated;

the decoupling valve member is further provided with rounded elastomerprojections which are distributed over the entire first and second facesof said decoupling valve member, and which project towards respectiveones of the first and second gratings, the studs extending beyond saidround projections from the first and second faces of the decouplingvalve member;

the decoupling valve member is further provided with an outer peripheralrim projecting towards the first and second gratings from the first andsecond faces of the decoupling valve member, said peripheral rim beingflush with the rounded projections of said first and second faces;

the second chamber is filled with liquid and is defined at least in partby a flexible elastomer wall, a constricted passage putting the firstand second chambers into communication with each other;

the elastomer body is bell-shaped so that it diverges about a centralaxis between a top secured to the first strength member and an annularbase secured to the second strength member, and the vibration-dampingsupport further comprises a deflector in the form of an annular ringthat extends inside the first chamber by surrounding the first gratingand by converging towards the top of the elastomer body, saidconstricted passage opening out in the first chamber outside thedeflector;

the first and second gratings are part of a rigid partition whichseparates the first and second chambers, the deflector including anabutment margin which extends parallel to said rigid partition and whichis clamped between the base of the elastomer body and said rigidpartition;

the deflector converges towards a flat top extending substantiallyparallel to the first and second gratings, the flat top having anannular rim which extends over a certain width and which surrounds anopening itself having a certain diameter, the width of the rim lying inthe range 2% of the diameter of the opening to 5% of the diameter of theopening.

In addition, in a second aspect, the invention relates to a hydraulicvibration-damping support serving to interconnect first and second rigidelements so as to damp and filter vibration between said elements, thesupport comprising:

first and second rigid strength members serving to be fixed torespective ones of the first and second rigid elements to beinterconnected;

an elastomer body that is substantially bell-shaped, extending about acentral axis between a top secured to the first strength member and anannular base secured to the second strength member;

a working chamber filled with liquid and defined at least in part by theelastomer body;

a compensation chamber filled with liquid and defined at least in partby a flexible elastomer wall;

a rigid partition that separates the working chamber from thecompensation chamber, which rigid partition comprises a sheet metalfirst piece that is in leaktight contact with the annular base of theelastomer body, and a rigid second piece that is in leaktight contactwith said sheet metal first piece and that co-operates with the flexiblewall to define the compensation chamber, the sheet metal first piecebeing provided with a first central grating that communicates with theworking chamber, and the rigid second piece being provided with a secondcentral grating that communicates with the compensation chamber whileco-operating with the first grating to define a valve member recess;

a decoupling valve member disposed in the valve member recess to moveover a short stroke parallel to the central axis to close off the firstand second gratings; and

a constricted passage filled with liquid and that puts the workingchamber into communication with the compensation chamber, theconstricted passage being defined in part by the sheet metal first pieceand by the rigid second piece of the rigid partition, said constrictedpassage extending angularly around the decoupling valve member over alinear length that is greater than the perimeter of the rigid partition,and said constricted passage being made up of first and second stages,the first stage of the constricted passage being adjacent to the workingchamber and extending between a first end that communicates with theworking chamber and a second end that communicates with the secondstage, while the second stage of the constricted passage is adjacent tothe compensation chamber and extends between a first end whichcommunicates with the second end of the first stage and a second endwhich communicates with the compensation chamber.

A hydraulic vibration-damping support of that type is disclosed, forexample, in Document FR-A-2 751 042, in which the rigid second piece ofthe rigid partition is a casting.

That known vibration-damping support is quite satisfactory as regardstechnical operation. In particular, it is known that the resonancefrequency of the constricted passage, which resonance frequency is alsothe frequency at which the vibration-damping support offers its bestperformance for large-amplitude vibration, depends on the ratio betweenthe length and the equivalent diameter of the constricted passage: byimplementing the constricted passage in two stages, it is thus possibleto obtain a passage length that is long and thus a resonance frequencythat is low for said constricted passage, which can be necessary incertain uses.

Unfortunately, the above-mentioned vibration-damping support suffersfrom the drawback that the casting of its rigid partition is relativelycostly to make, and also relatively weighty, which tends to increaseboth the cost and the weight of the vibration-damping support.

A particular object of the present invention is to mitigate thosedrawbacks.

To this end, in a vibration-damping support of the type in question:

the rigid second piece of the rigid shell is constituted by a secondpiece of sheet metal that is cut out and stamped;

the flexible elastomer wall is secured to a rigid base which is itselfsecured to the second strength member and which has at least one sidewall extending about the central axis from the second strength member toan inner annular abutment margin;

the second piece of sheet metal includes an outer annular abutmentmargin that is in leaktight contact with the inner annular abutmentmargin of the base, the second piece of sheet metal further including astep which extends about the central axis from said outer annularabutment margin to a non-perforated annular zone that is in leaktightcontact with the first piece of sheet metal, the second stage of theconstricted passage being defined between the first piece of sheetmetal, the side wall of the base, the inner annular abutment margin ofthe base, the outer annular abutment margin of the second piece of sheetmetal, and the step of said second piece of sheet metal;

and the first stage of the constricted passage is defined between theannular base of the elastomer body, and the first piece of sheet metal.

By means of these provisions, it is possible to obtain a constrictedpassage that is very long, extending over two stages, by using apartition that is merely made up of two pieces of sheet metal, and thatis therefore particularly lightweight and inexpensive.

In preferred embodiments of the vibration-damping support the invention,it is optionally possible, in addition, to use any of the followingprovisions:

the second strength member includes an annular inner portion which ispart of the base of the elastomer body and which forms a groove that isopen facing towards the first piece of sheet metal, said grooveco-operating with said first piece of sheet metal to define the firststage of the constricted passage, the first and second ends of the firststage of the constricted passage being separated from each other by anelastomer stopper that is part of the elastomer body;

the first piece of sheet metal is provided with an outer annular rimthat extends about the central axis towards the second strength memberto a free annular edge that is applied axially in leaktight contactagainst an outer portion of the second strength member, the innerportion of the second strength member being provided with an inner skirtthat is extended parallel to the central axis beyond said free annularedge to come into contact with a radial annular portion that is part ofthe first piece of sheet metal, the first stage of the constrictedpassage being defined in part by said inner skirt and by said outer rimof the first piece of sheet metal;

the first piece of sheet metal includes a non-perforated annular portionwhich is in leaktight axial contact with the second piece of sheet metaland which is extended inwards by an annular step that is itself extendedby the first grating, the valve member recess being defined laterally bysaid annular step of the first piece of sheet metal;

the first stage of the constricted passage communicates with the secondstage of the constricted passage via an opening cut out in the firstpiece of sheet metal, and the second stage of the constricted passagecommunicates with the compensation chamber via an opening cut out in thesecond piece of sheet metal;

the opening cut out in the second piece of sheet metal is provided atleast in the outer annular abutment edge and in the step of said secondpiece of sheet metal, the first and second ends of the second stage ofthe constricted passage being separated from each other by an elastomerstopper molded integrally with the flexible elastomer wall against aninner face of the inner abutment margin and an inner face of the sidewall of the base, said elastomer stopper of the base penetrating in partinto the opening in the second piece of sheet metal, and the secondgrating having a non-perforated portion that is applied axially inleaktight contact against said elastomer stopper of the base;

the elastomer stopper of the base is provided with a slot that is openaxially towards the elastomer body and laterally towards the first endof the second stage of the constricted passage, the step of the secondpiece of sheet metal having an edge that laterally defines the openingcut out in said second piece of sheet metal and that penetrates intosaid slot;

the flexible elastomer wall is molded over the base so that it formsextra thickness in the vicinity of the elastomer stopper of the base,the opening cut out in the second piece of sheet metal forming two edgesin the outer annular abutment margin of said second piece of sheetmetal, the two edges being disposed on either side of the elastomerstopper of the base and on either side of said extra thickness; and

the elastomer stopper of the base is provided with a stud that projectsaxially towards the elastomer body, and the first piece of sheet metalincludes a portion that comes into leaktight axial abutment against theelastomer stopper of the base, and that is provided with a hole in whichthe stud is engaged.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention appear from thefollowing description of an embodiment of it given by way ofnon-limiting example and with reference to the accompanying drawings.

In the drawings:

FIG. 1 is a vertical section view through a vibration-damping support inan embodiment of the invention;

FIGS. 2 and 3 are perspective views of respective ones of the two facesof a decoupling valve member that is part of the vibration-dampingsupport of FIG. 1;

FIG. 4 is a graph showing the dynamic stiffness of the vibration-dampingsupport of FIG. 1 as a function of frequency, compared with the dynamicstiffness of the same vibration-damping support equipped with adecoupling valve member with no studs and no deflector in its workingchamber;

FIGS. 5 and 6 are exploded perspective views of the vibration-dampingsupport of FIG. 1; and

FIGS. 7 and 8 are detail perspective views of two portions of thevibration-damping support of FIG. 1, one of which comprises acompression-resistant elastomer body, the other portion comprising anelastomer bellows.

MORE DETAILED DESCRIPTION

In the various figures, like references designate identical or similarelements.

FIG. 1 shows a hydraulic vibration-damping support 1 having first andsecond strength members 2, 3 which, for example, serve to be fixedrespectively to the engine-and-gearbox unit and to the body of avehicle.

In the example in question, the first strength member 2 is in the formof a metal block made of a light alloy, for example. The metal block iscentered on a vertical axis Z and it is secured to a threaded pin 4making it possible, for example, to fix the block to theengine-and-gearbox unit.

The second strength member 3 is formed by a ring of cut-out and stampedsheet metal, also centered on the axis Z. In the example shown, thesecond strength member 3 has an outer portion 5 that extends in a radialplane about the axis Z and that serves, for example, to be fixed to thebody of the vehicle, and an inner portion 6 that is recessed, that is ofsubstantially upside-down U shaped cross-section, and that forms anannular groove 33 that is open axially facing away from the firststrength member 2. The inner portion 6 also forms an axial inner skirt 6a that extends downwards further than the outer portion 5.

The two strength members 2, 3 are connected together via a relativelythick elastomer body 7 which is sufficiently compression resistant totake up the static forces due to the weight of the engine-and-gearboxunit. The elastomer body 7 has a bell-shaped side wall that extendsbetween a top 8 molded over the first strength member 2, and an annularbase 9 which is molded over the bottom portion 6 of the second strengthmember 3.

In addition, the second strength member 3 is secured to a limiting cap10 that is made of sheet metal, that is annular in shape, and thatcovers the elastomer body 7 with clearance being left, and with apassageway being left for the pin 4. The cap 10 thus limits the relativemovement between the first and second strength members 2, 3.

The second strength member 3 is also secured to a rigid partition 11which co-operates with the elastomer body 5 to define a first chamber Afilled with liquid and referred to as the “working chamber”.

In the example in question, the rigid partition 11 is made up of firstand second pieces of stamped sheet metal 12, 13 that are mutuallysuperposed and that are dish-shaped. In their central portions, theyrespectively form first and second flat gratings 14, 15 which areprovided with holes 16 and which extend perpendicularly to the centralaxis Z.

For example, the first piece of sheet metal 12 comprises:

an annular rim 17 which extends parallel to the axis Z, and which has afree top annular edge 18 in leaktight abutment against a layer ofelastomer 19 which is part of the elastomer body 7 ANC which isovermolded under the outer portion 5 of the second strength member;

an annular portion 20 which extends radially inwards from the bottom endof the rim 17, the inner skirt 6 a of the second strength member beingin leaktight abutment against said annular portion 20;

a step 21 which extends towards the working chamber A from the radiallyinnermost edge of the annular portion 12; and

said first grating 14 which extends the step 21 radially inwards.

In addition, in the example in question, the second piece of sheet metal13 comprises:

an annular outer abutment margin 22 which extends radially relative tothe central axis Z;

an annular step 23 which extends axially parallel to the axis Z towardsthe first piece of sheet metal 12; and

said second grating 15 which has an outer periphery in abutment underthe annular portion 20 of the first piece of sheet metal 12.

The vibration-damping support 1 further includes a base 24 made ofcut-out and stamped sheet metal and comprising:

an annular abutment margin 25 which is fixed to the outer portion 5 ofthe second strength member, e.g. by crimping, and which is in leaktightabutment against said layer of elastomer 19 under the outer portion 5 ofthe second strength member;

an axial annular side wall 26 which extends from the inner periphery ofthe abutment margin 25 parallel to the axis Z and going away from thesecond strength member 3;

a bottom abutment margin 27 which extends the bottom end of the sidewall 26 radially inwards; and

an axial rib 28 which extends axially away from the elastomer body 7from the radially innermost portion of the abutment margin 27.

The abutment margin 27 and the rib 28 of the base 24 are overmolded by aflexible bellows 29 which is made of elastomer, which also forms a layer30 of elastomer covering the abutment margin 27 of the base, and againstwhich the abutment margin 22 of the second piece of sheet metal 13 comesinto leaktight abutment.

Thus, the bellows 29 co-operates with the partition 11 to define asecond chamber B referred to as a “compensation chamber” and filled withliquid.

The compensation chamber B communicates with the working chamber A viaan annular constricted passage C which extends over substantially twoturns and over two stages around the chambers A and B, namely:

a first stage C1 which communicates with the working chamber A via anopening 31 obtained by means of a cutout 32 provided in the inner skirt6 a of the second strength member, and by means of a correspondingrecess in the base 9 of the elastomer body, the first stage C1 of theconstricted passage being defined between the first piece of sheet metal12 and the annular groove 33 provided in the base 9 of the elastomerbody, inside the recessed inner portion 6; and

a second stage C2 which is defined by the first and second pieces ofsheet metal 12, 13 and by the side wall 26 of the base, the second stageC2 communicating with the first stage C1 via an opening 34 provided inthe first piece of sheet metal 12 (see FIG. 5), and said second stage C2further communicating with the compensation chamber B via an opening 35provided in the second piece of sheet metal 13 (see FIG. 6).

In addition, the vibration-damping support 1 also includes a decouplingvalve member 37 (shown in FIGS. 1 to 3) which is mounted with a smallamount of clearance (e.g. approximately in the range 0.5 millimeters(mm) to 1 mm) between the first and second gratings 14, 15.

This decoupling valve member is in the form of an elastomer pad which issuitable for vibrating between the first and second gratings 14, 15 bybeing applied alternately against the two gratings and by closing themoff when the first and second strength members 2, 3 undergo relativevibratory movements.

On its first and second faces 38, 39, the decoupling valve member 37 hasprojecting elastomer studs 40 which are disposed to abut against thefirst and second gratings 14, 15 so that, in the absence of relativevibration between the first and second strength members 2, 3, the valvemember 37 has a midplane P that is disposed on a slant relative to thefirst and second gratings 14, 15.

When the decoupling valve member is subjected to vibration, the studs 40are suitable for being flattened under the effect of the pressure of theliquid in the chambers A, B which communicate respectively with thefirst and second faces 38, 39 of the decoupling valve member via thefirst and second gratings 14, 15. Thus, the peripheral rim 41 of thevalve member can thus come to press in leaktight manner against thenon-perforated annular portions 14 a, 15 a surrounding the holes 16 ofthe gratings 14, 15.

In addition, the valve member 37 is advantageously provided withcentering lugs 42, 43 which co-operate by mutual engagement with thegratings 14, 15 to center the decoupling valve member 37. In the exampleshown, the first centering lug 42 is hemispherical in shape and itpenetrates into a hole 14 b in the first grating 14, while the secondcentering lug 43 is clipped into a hole 15 b in the second grating 15,the second centering lug 43 having an enlarged head 43 a whichpenetrates into the compensation chamber B.

As shown in more detail in FIGS. 2 and 3, the studs 40 that cause thedecoupling valve member to be in an inclined position are preferablydisposed close to the outer periphery of the decoupling valve member,and are referred to below as “outer studs”.

The outer studs 40 of the decoupling valve member are preferablydistributed in first and second groups of outer studs 40. The outerstuds 40 of the first group are disposed on the first face 38 only, onone side only of a geometrical construction line passing across thedecoupling valve member parallel to the midplane P of said decouplingvalve member, while the outer studs 40 of the second group are disposedon the second face 39 only of the decoupling valve member, on the otherside of said construction line.

In the example in question, the decoupling valve member 37 is in theshape of a disk and the construction line in question is a diametricalaxis Y substantially perpendicular to the central axis Z and passingthrough the center O of the valve member.

In the example shown, the first group of outer studs comprises threeouter studs 40, one of which is disposed in alignment with an axis Xpassing through the center O of the valve member and perpendicular tothe axis Y (the axes X and Y defining the above mentioned midplane P ofthe decoupling valve member), while the other two outer studs 40 of thefirst group are disposed substantially at 60° from the axis X about thecenter O of the decoupling valve member.

In addition, also in the example shown, the second group of outer studsalso comprises three outer studs 40 which are disposed substantiallysymmetrically to the outer studs 40 of the first group about the axis Y.Thus, the outer studs 40 of the second group also include an outer studthat is aligned with the axis X and two outer studs that are disposedsubstantially at 60° from the axis X about the center O of thedecoupling valve member. The outer studs 40 of the first and secondgroups are disposed in the vicinity of the above-mentioned outer rim 41of the decoupling valve member, which outer rim 41 projects towards thegratings 14, 15 from the two faces 38, 39 of the decoupling valvemember. However, the outer studs 40 extend beyond the outer rim 41towards the gratings 14, 15.

By means of these provisions, and in particular because of the inclinedposition of the valve member imposed by the outer studs 40, banging ofthe valve member against the gratings is reduced significantly and thedynamic stiffness of the vibration-damping support is reduced at highfrequencies.

Advantageously, in order to contribute to improving the acousticperformances of the vibration-damping support further, it is alsopossible to make the following provisions:

it is possible to provide the first face 38 of the decoupling valvemember with two inner studs 44 disposed in the vicinity of the centeringlug 42 and having, for example, the same size as the outer studs 40, theinner studs 44 being, for example, disposed in alignment with the centerO of the valve member along the axis X;

it is possible to provide the second face 39 of the decoupling valvemember with two inner studs 45 situated in the vicinity of the centeringlug 43 and disposed, for example, on the side of the axis Y opposite toits side on which the outer studs 40 of the second group are situated,the inner studs 45 being, for example, disposed symmetrically about theaxis X so that each of them forms an angle of about 60° with the axis Xabout the center O of the valve member; and

it is possible to provide both faces 38, 39 of the decoupling valvemember with rounded projections 46 that project respectively towards thefirst and second gratings 14, 15, preferably by being flush with the rim41, and in any event without projecting beyond the studs 40, 44, 45.

It should be noted that the faces 38, 39 of the valve member 37 could beinverted without going beyond the ambit of the invention.

Advantageously, the vibration-damping support 1 further includes adeflector 47 in the form of an annular ring centered on the axis Z, andwhich extends inside the working chamber A by surrounding the firstgrating 14 and by converging towards the top 8 of the elastomer body.The opening 31 via which the constricted passage C opens out into theworking chamber A lies radially outside the deflector 47.

In the example shown, the deflector 47 has an abutment margin 48 whichextends radially relative to the axis Z and which is clamped axiallybetween the base 9 of the elastomer body and the annular portion 20 ofthe first piece of sheet metal 12. The abutment margin 48 is extendedradially inwards and axially towards the top 8 of the elastomer body bya side wall 49 which, in the example shown is frustoconical, by formingan angle α lying, for example, in the range 15° to 35° with the axis Z.The side wall 49 is itself extended, at its top end, by a flat rim 50which extends substantially radially inwards and which defines acircular opening 51. The width of the rim 50 lies, for example, in therange 2% of the diameter of the opening 51 to 5% of the diameter of theopening 51.

By means of the above-described provisions, the acoustic characteristicsof the vibration-damping support 1 are improved very significantly, andin particular its dynamic stiffness K at high frequencies is improvedvery significantly.

In particular, FIG. 4 shows, as an uninterrupted line, the curve 52 ofthe dynamic stiffness K of the vibration-damping support along the axisZ as a function of frequency F, and, as a dashed line, the curve 53 ofthe dynamic stiffness of the same vibration-damping support 1 but asprovided with a conventional decoupling valve member and as not providedwith a deflector 47.

It can be seen from FIG. 4 that the vibration-damping support of theinvention makes it possible to avoid a stiffness peak 54 that ischaracteristic of prior art vibration-damping supports. That stiffnesspeak corresponds to acoustic vibration being transmitted between theengine and the body of the vehicle.

It should be noted that both the decoupling valve member 37 of theinvention and the deflector 47 of the invention procure advantageouseffects on the acoustic characteristics of the vibration-damping supportand that, optionally, each of these two elements may be usedindependently from the other.

In other words, the deflector 47 may be used effectively with adecoupling valve member other than the above-described decoupling valvemember 37, and the above-described valve member 37 may be usedadvantageously in the absence of the deflector 47.

However, the inventors of the present invention have observed that bycombining the decoupling valve member 37 of the invention with thedeflector 47 of the invention, it is possible to procure advantageouseffects that are considerably greater than the effects that can beexpected in view of the effects procured by the valve member 37 inisolation, and of the effects procured by the deflector 47 in isolation.

In addition, it should be noted that the embodiment of the constrictedpassage C described above is particularly inexpensive insofar as saidembodiment makes it possible to obtain a constricted passage C that islong, extending over two turns, without having to use a light alloycasting, as is usually necessary.

The way in which the constricted passage is implemented in the examplein question is shown in more detail in FIGS. 5 to 8:

as shown in FIGS. 5 and 7, the elastomer body 7 forms an elastomerstopper 55 which closes off the first stage C1 of the constrictedpassage between firstly the opening 31 that puts the constricted passageinto communication with the working chamber A, and secondly the opening34 that is cut out in the annular rim 17 and in the annular portion 20of the piece of sheet metal 12 to put the first and second stages C1, C2of the constricted passage into communication with each other; and

the elastomer bellows 29 is molded integrally with an elastomer stopper56 that is shown clearly in FIGS. 6 and 8 and that closes off the secondstage C2 of the constricted passage between the above-mentioned opening34 and the opening 35 that puts the second stage C2 into communicationwith the compensation chamber B, the opening 35 being cut out in theabutment margin 22, in the step 23, and in the outer periphery of thenon-perforated annular portion 15 a of the second piece of sheet metal13.

Thus, the liquid which passes from the working chamber A to thecompensation chamber B follows the entire length of the constrictedpassage C, firstly following the first stage C1 in one angulardirection, then the second stage C2, preferably in the same angulardirection.

It should be noted that assembly of the first and second pieces of sheetmetal 12, 13 in the vibration-damping support is made easier, in theexample in question, by the following provisions:

the edges 22 a of the abutment margin 22, which edges define in part thecut-out 35 in the second piece of sheet metal 13, come into engagementon either side of the elastomer stopper 56 and of an extra thickness ofelastomer 57 molded integrally with said elastomer stopper (see FIGS. 6and 8);

the stopper 56 has an abutment surface 56 a lying in a radial plane andagainst which a segment of the non-perforated annular portion 15 a ofthe grating 15 comes to bear in leaktight manner, which segment issituated in the vicinity of one of the edges 23 a of the step 23 of thesecond piece of sheet metal 13, so that the elastomer stopper 56 closesoff a portion of the opening 35, thereby separating said opening 35 fromthe opening 34 that communicates with the first stage C1 of theconstricted passage;

the edge 23 a of the step 23, which edge defines the opening 35 in partopposite from the non-closed-off portion of said opening, is offsettowards the inside of said opening 35 relative to the corresponding edge22 a of the abutment margin 22, and said edge 23 a comes into engagementin a circularly arcuate slot 58 centered about the axis Z, said slot 58being provided in the elastomer stopper 56, opposite from the portion ofthe opening 35 that is left free by the stopper 56;

the elastomer stopper 56 is advantageously provided with a centeringstud 59 extending axially towards the first piece of sheet metal 12 andengaging into a corresponding hole 60 in said first piece of sheetmetal; and

the abutment margin 25 of the base and the outer portion 5 of the secondstrength member are not circularly symmetrical in shape, so as todetermine the angular positions of these two parts relative to eachother during assembly.

What is claimed is:
 1. A hydraulic vibration-damping support serving to interconnect first and second rigid elements so as to damp and filter vibration between said elements, the support comprising: first and second rigid strength members serving to be fixed to respective ones of the first and second rigid elements to be interconnected; an elastomer body interconnecting the first and second strength members; a first chamber filled with liquid, and defined at least in part by the elastomer body; and a decoupling device comprising firstly first and second parallel gratings that are generally plane in shape, and secondly a decoupling valve member which is in the form of an elastomer pad and which has first and second faces provided with projecting studs made of elastomer, the decoupling valve member being mounted with clearance between the first and second gratings with the first and second faces of said decoupling valve member disposed facing respective ones of the first and second gratings, and said decoupling valve member being suitable for closing off said gratings, said first grating communicating with the first chamber and the second grating communicating with a second chamber suitable for enabling the decoupling valve member to vibrate freely between the two gratings when the first and second strength members are subjected to relative vibratory movements; wherein the studs of the decoupling valve member are disposed so that, in the absence of relative vibration between the first and second strength members, the decoupling valve member is held in a rest position in which said valve member has a midplane disposed on a slant relative to the first and second gratings.
 2. A vibration-damping support according to claim 1, in which the studs of the decoupling valve member comprise outer studs which are disposed in the vicinity of an outer periphery of said decoupling valve member and which are distributed in first and second groups of outer studs disposed on either side of a geometrical construction line extending across the decoupling valve member parallel to the midplane of said decoupling valve member, the first group of outer studs being situated on the first face, and the second group of outer studs being situated on the second face of said decoupling valve member.
 3. A vibration-damping support according to claim 2, in which the decoupling valve member is in the shape of a circular disk having a center through which a diametrical line constituting said construction line passes.
 4. A vibration-damping support according to claim 2, in which the outer studs of the first group are symmetrical to the outer studs of the second group about said construction line.
 5. A vibration-damping support according to claim 2, in which the decoupling valve member is provided with first and second elastomer centering lugs disposed at the center of the decoupling valve member on respective ones of the two faces of said decoupling valve member, said first and second centering lugs co-operating with respective ones of the two gratings to center the decoupling valve member relative to said gratings, the studs of the decoupling valve member further comprising inner studs disposed in the vicinity of the center of said decoupling valve member on both faces of said decoupling valve member.
 6. A vibration-damping support according to claim 5, in which the decoupling valve member is provided with two inner studs disposed in the vicinity of the first centering lug, symmetrically about said construction line.
 7. A vibration-damping support according to claim 5, in which the second centering lug is clipped into one of the gratings, and the decoupling valve member is provided with two inner studs disposed close to the second centering lug, on the side of said construction line opposite to its side on which the outer studs of the second group are situated.
 8. A vibration-damping support according to claim 1, in which the decoupling valve member is further provided with rounded elastomer projections which are distributed over the entire first and second faces of said decoupling valve member, and which project towards respective ones of the first and second gratings, the studs extending beyond said round projections from the first and second faces of the decoupling valve member.
 9. A vibration-damping support according to claim 8, in which the decoupling valve member is further provided with an outer peripheral rim projecting towards the first and second gratings from the first and second faces of the decoupling valve member, said peripheral rim being flush with the rounded projections of said first and second faces.
 10. A vibration-damping support according to claim 1, in which the second chamber is filled with liquid and is defined at least in part by a flexible elastomer wall, a constricted passage putting the first and second chambers into communication with each other.
 11. A vibration-damping support according to claim 10, in which the elastomer body is bell-shaped so that it diverges about a central axis between a top secured to the first strength member and an annular base secured to the second strength member, and the vibration-damping support further comprises a deflector in the form of an annular ring that extends inside the first chamber by surrounding the first grating and by converging towards the top of the elastomer body, said constricted passage opening out in the first chamber outside the deflector.
 12. A vibration-damping support according to claim 11, in which the first and second gratings are part of a rigid partition which separates the first and second chambers, the deflector including an abutment margin which extends parallel to said rigid partition and which is clamped between the base of the elastomer body and said rigid partition.
 13. A vibration-damping support according to claim 11, in which the deflector converges towards a flat top extending substantially parallel to the first and second gratings, the flat top having an annular rim which extends over a certain width and which surrounds an opening itself having a certain diameter, the width of the rim lying in the range 2% of the diameter of the opening to 5% of the diameter of the opening. 